Electric motor construction that was developed in the 1800s uses a fixed placement of magnetic fields to initiate an electromotive force (EMF). An increase of electrical current induces a larger or stronger magnetic field causing a greater electromotive force at a higher and less efficient consumption rate. Therefore, a motor supplied with increased electrical current is limited to a particular RPM peak by a back EMF.
High temperature superconductors have been used to design electric motors due to their high current density and low DC losses. Such motors require cryogenic cooling systems to keep the temperature of the superconductors from rising too high.
A large portion of the electromagnetic energy lost by an electric motor is due to hysteresis and eddy currents. Hysteresis loss refers to the amount of electro-magnetic energy absorbed by ferrous metal when its magnetization is changed by the application of an alternating magnetic field. Eddy currents are currents unintentionally induced in conductive motor components by the fields in the motor. These currents produce magnetic fields opposite of those that operate the motor, and thus act as a form of magnetic drag on the motor. Thus, there is a need for an electric motor that decreases the energy losses due to these issues and provides increased efficiency.